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Question about V1 Vr V2 computations
On ASA’s ATP test book they mention the following: “V1 is computed using the actual airplane gross weight, flap setting, pressure altitude and temperature.” I understand that v1 gets adjusted for slope and winds too but they didn’t mention anything about Vr and V2.
Is my conclusion right? v1 vr and v2 are computed using the aircraft’s weight, flap setting, temperature, and pressure altitude. The difference is that V1 gets adjusted for winds and slope, and vr v2 don’t.
Thank you!

That's correct.
V1 has to do with acceleration and stopping, and both of those are affected by headwind/tailwind and runway slope.
VR is the (air) speed at which you want to start flying, and so head/tailwind won't change that speed (although it will change the groundspeed you're moving when you rotate). And runway slope won't affect this speed either.
V2 is a climb speed, so it happens in an airmass, and isn't affected by what the ground below is doing, neither in terms of slope nor wind (i.e. the difference of a moving airmass vs a stationary airmass).
The exception to all of this... enhanced climb. This is a bit of an advanced topic, where you use more runway to get moving faster, and then your climb performance airborne is better than it would have been. In this case, the performance engineers compute a higher than normal VR. With ample runway, your V1 can go up to match VR, and the V2 speed is (somewhat artificially) raised to be a few knots above VR. And because of all the computations involved, all of these can be affected by winds & slope.
But: for a straightforward understanding of V1, VR, and V2, it's safe to say that only V1 is affected by winds and runway slope.


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Question about ILS approach categories
I was reading about FAAs ILS approach categories minimums and have a question!
Category II. DH 100 feet and RVR 1,200 feet (with autoland or HUD to touchdown and noted on authorization, RVR 1,000 feet);
To what authorization it refers? To an authorization placed in the remarks section of the instrument approach allowing a CAT II approach to have a RVR as low as 1000 feet if the pilot uses a HUD to touchdown for example?
Thanks!

The note you are referring to
RVR 10 authorized with specific OPSPEC, MSPEC, or LOA approval and use of autoland or HUD to touchdown
The FAA must authorize the operator to use a lower RVR for CAT II approaches.  The FAA would review the training program and ensure adequate check pilots are approved to validate the training program and authorize the crew to use RVR 10.
See https://www.ecfr.gov/current/title-14/section-61.67

Thank you! And in the instrument approach chart the minimums would have a RVR of 1000 FT along with a note stating that a minimum equipment and aircrew certification is required right?

@Breaach  The authorization would be in the company's OPSPEC (or their MSPEC, if they use that, or a specific Letter of Authorization from the FAA to that company). As I understand it, if you're authorized for Cat III, you can use your Cat III procedures with the Cat II chart & 1,000 RVR. Otherwise, the higher (probably 1,200 RVR) mins on the chart apply..

Usually the approach chart shows the minimums that are approved for everyone.  If they minimums are lower for some specific reason, there will be a note on the new minimums and the method to be authorized down to the new mins.

source: Stack Exchange

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What is the definition of Height Above Threshold (HAT)?
I could use some help settling a disagreement about the definition of HAT.
So my company uses the word HAT to mean “height of the aircraft above TDZE…at any given distance…at any given time”
So as an example, on an approach if you’re 20 miles out at 6000’ … then your HAT = 6000’ (assuming TDZE=0). Then if you’re 10 NM out at 3000’ then your HAT = 3000’.
So based on my understanding of the AIM’s definition of HAT, the above example is an incorrect use of the word HAT. HAT is a charted number on a plate, and it’s fixed. For the individual approach being flown, HAT does NOT change as the aircraft altitude changes. It does not reflect the aircraft altitude above TDZE, any ANY given distance.
Am I wrong?

The height above touchdown (HAT) is the height of something (e.g. the aircraft, or a procedural height) measured relative to the elevation of the touchdown zone. Note that this is similar to but crucially different from above ground level (AGL).
When listed as AGL, the height is measured relative to the elevation of the underlying terrain, and thus the position of the aircraft over the non-flat terrain plays a role in the conversion between MSL and AGL.
When converting between MSL and HAT, the terrain profile does not play a role.
The decision height on the map is given as HAT, not as AGL.
Suppose there is an up-slope in the terrain towards the threshold of the runway. The decision height is at 200' HAT, but due to the lower terrain on short final, this decision height will be crossed at 300' AGL (as measured by the radio altimeter).

HAT is published on instrument approaches to show the AGL altitude the aircraft would be at when crossing the MDA or DA.
Your company is using the HAT concept to help determine if they are on a standard glidepath or 300 FT/NM + HAT.  On a visual approach, this would be a good method as a backup on whether or not they are trending high or low.
Interestingly enough, non-precision approaches in Europe use a similar concept with charted altitudes every mile to stay on a certain glidepath.

No my company is trying to say HAT indicates the aircraft altitude above the airport at ANY and all distances from the field (nit just at DA). So for example… at 20 miles out and 6000’, their definition of HAT is 6000. Then at 3000’ the HAT changes to 3000. That’s how my company uses HAT. So you agree that’s incorrect usage of HAT, yes?

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Why do turboprops not have a thrust value in the specifications?
When looking through aircraft engine specifications, turbofans always provide a thrust value, e.g. in JT8D engine: https://prattwhitney.com/products-and-services/products/commercial-engines/jt8d
In constrast, turboprops do not provide this value, see PT6A engine page: https://www.pwc.ca/en/products-and-services/products/general-aviation-engines/pt6a
Why is this the case?

It's a bit of a historical reason. In the olden days of only piston engines powering aeroplanes, the unit of measurement for the capability of the engine was the Brake Horse Power BHP. The engine powers the propeller, and with data on propeller blades and airspeed the resisting torque can be determined - the determining equations are of a rotary and variable nature, like those powering the tyres of an automobile.

When the first jet engines were designed around WW2 like the Junkers Jumo above, there was no external device to power up. Enabling the aeroplane to fly was a stream of exhaust gases, which provided thrust in an amount that was relatively constant over airspeed. So turbojet capability was expressed in kgf, lbs or whichever olden days unit, now kN of course. Much more convenient for computing aeroplane speed.
Nowadays most larger aircraft are powered by turbine engines. When they power a propeller or helicopter rotor, it still makes sense to consider the rotary output shaft power as one of the inputs for the thrust equations. Propeller tip speed, number of blades, airspeed, blade angle would be some other inputs, with constant speed propellers adjusting the blade angle automatically to provide optimum thrust from the available power.

When the turbine powers a fan there is still a propelling stream of exhaust gases generated by the engine, but the situation is not as clear as in case of the turbojet. Graph above is from prof. Wittenberg's TU Delft book VTH-D 14, and plots the thrust ratio over speed for various bypass ratios $\lambda$. The pure turbojet of $\lambda$ = 0 is indeed relatively constant over airspeed, higher bypass ratios are not. Turbofan thrust is a variable of airspeed, like propeller thrust is.
So would it make sense to express the turbofan potency in kW, since the fan looks a lot like a propeller? For two reasons it does not:

Maximum thrust is required at TakeOff
The fan has no variable blade incidence, or gearing from engine output shaft to fan RPM.

In order to compute the aircraft speed/altitude capabilities we need the available thrust. Turbofan power is still expressed in kN despite the variability over airspeed, turboprop power in kW shaft output despite the constant speed implementation - a historical reason.

Because the turbofan's thrust value is derived from the integrated fan unit that is part of the engine.  It's all an integrated product of the engine manufacturer.
A turboprop's thrust making component, the propeller, is a separate item completely, and the thrust the propeller can produce, for a given input torque and RPM, will vary from propeller design to propeller design, there being numerous variables within different propeller configurations.
If P&W built the PT6 with a specific propeller with specific characteristics, and that was the ONLY propeller that could be used, then P&W could provide a thrust specification for that engine/propeller.  But since they don't make the propeller, they only specify what they can specify for the engine itself independent of the prop, which is the engine's torque and horsepower.

... and that PT-6 thrust would only be valid for one type of installation and one airspeed. Power will be nearly constant over speed and fairly independent of the cowling shape around the engine.

Although power output for most turboprops is listed in Equivalent Shaft Horsepower (ESHP), which is an effective sum of both the mechanical power output of the driveshaft and reaction thrust from the exhaust stubs.

@PeterKämpf well if you were going to quote a value it would likely be actual measured static thrust at (or converted to) sea level, ISA, using a live a/c or an engine/cowl in a test cell.


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Typical maximum airliner throttle settings during taxi
What is the typical maximum throttle setting during taxi of a big airliner, e.g., A350, B777, etc.?
Thank you.
Fabián

Probably idle once you are rolling.  Just enough to get moving and not blow people over before that.  Actual power setting during taxi isn't something pilots normally really focus on.  It's not like setting T/O, climb, or cruise power...

For 737 you go for max 30% N1 to get some acceleration after getting the airplane into motion, IDLE thrust will do.


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Do I need any authorization to work and sign out performed maintenance on US-registered general aviation aircraft outside of USA?
I'm non-USA citizen and holder of FAA A&P Mechanic's certificate but haven't worked on US-registered aircraft since 1999 however all this time I'm involved in commercial aircraft maintenance and CAMO activities and currently have more than 6 months experience within the preceding 24 months on non-US registered aircraft under other country's CAA authorization. My questions are:

Do I have to apply to FSDO to exercise privileges of my FAA certificate or is it considerable as current?
To carry out maintenance on US-registered general aviation aircraft (Piper Aztec) outside of USA, do I have to have any special authorization from FAA?

Thank you in advance
Giorgi


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Reasons for ADSB PAPR Report Altitude Errors
We have just test flown a new 1090 ADSB installation, using Apareo Stratus ESG Transponder, which has internal GPS.
The PAPR for the test flight show both Baro Alt and Geo Alt errors in the Missing Elements Table. The MCF count is identical for both, and the %Fail percentage is 8.27%.
All ground testing has been successful, both before and after the test flight.
I have studied the FAA PAPR User's guide and understand what the
I would appreciate any thoughts on the possible reasons for these errors.

Try to spell out less common abbreviations at least once in the question or comment. What error do you want feedback about? You only say there is an altitude error but you do not tell us exactly what that error is.

In the ADS-B velocity message (Field Type Code 19, IIRC), the geometric altitude is encoded as difference from the barometric altitude. If barometric altitude is not available, the difference cannot be computed.
Based on this, I deduct that the problem lies in the barometric altitude source connected to the transponder. In 8.7% of the messages that did not provide a valid altitude to the transponder, resulting in both pressure altitude and geometric altitude becoming unavailable.
I would have the connection between the altitude encoder and the transponder and the encoder itself checked out.


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What's the type of screen for the PFD/ND on the 737?
What's the type of screen used on the Boeing PFD and ND displays?
It doesn't seem to be LCD - because for one they didn't have them when these planes were certified and the resolution seems to be so good. Even better than a 4K LCD display.
I assume it's some type of CRT.
But how does one create text on a CRT with such high resolution - the text's are so clear even close up.

I am not familiar with the 737, but I can say the early Airbus CRTs were hybrid vector-raster CRTs. That is, when drawing lines and text, the e-beam traces the lines, so there are no pixels. When drawing fills, like the horizon, those are rastered. This was done for maximum brightness. Step through this YouTube video of an A300 to see how it's done.

Yes that's my initial thought. When I look at the real display it looks like a crt (but it's not concave) - but the lines and text are very sharp. even up close (6 inches or so) - no pixelation.

The reason why you aren't seeing a curve is that the DUs have a dark tinted piece of glass in front of the CRT tube, the same as the anti-glare filters people used to use on their computer monitors. Underneath, the actual tube has a curve and has a lighter gray background.

As @mins indicated there are retrofit LCD displays available for the B737 Classic.
The 737NG series aircraft were initially certificated with CRT displays. As CRT technology became obsolescent and very quickly non-procurable in the late 1990's Boeing needed to address the issue for both existing aircraft and future production.
Rockwell Collins was the B737NG display system supplier and developed an LCD Display Unit (DU) to replace the earlier CRT DU. These became the standard production DUs about 1999 (less than two years after the NG's entry into service). As they were certificated in the aircraft, they were also available to replace the CRT DUs in earlier production aircraft.
There were concerns by the FAA at the time about mixing DU types on the flight deck. The solution was to replace all DUs with LCD DUs if one of the CRT DUs failed and there was no spare CRT DUs available.
A similar issue existed for the B747-400. Due the the different economy of scale, they made the effort to certificate the use of mixed display types. That was around 2001.
By 2002, the 737 Aircraft Maintenance Manual makes no reference to the CRT displays:

Display Unit
The display unit (DU) is a flat panel liquid crystal display (LCD)
unit. The LCD makes a high resolution color image of the flight data.

I'd be curious to know what the resolution of these screens are (i.e. PPI). I've set up a sim display using a 4K display and I can still see the jaggies. The text and lines on these displays have no jaggies and super clear.

@dashman Ultra-high resolution LCD displays have definitely been a thing since at least the late-1990s (for example, the truly epic IBM T221 from 2001 was a 22-inch display with a 204dpi display at 3840x2400 (slightly bigger than 4K). Back then, desktop computers really couldn't handle anything besides 96dpi, so there was no incentive for anyone to make mass-market high-DPI displays until Windows caught-up with macOS's Retina around 2015. I also remember reading about high-DPI medical X-Ray display monitors too.

desktop computers really couldn't handle anything besides 96dpi No! They couldn't (except with special new video cards, as with the T221, etc.) handle such high total display sizes (3840x2400). But 96dpi? 2040dpi? Whatever! Windows (and most other OSes) can work with any size display. The issues are the number of pixels. To take an extreme - you can easily use a projector to get an 8' wide display - that might be on the order of 20 pixels per inch. No reason you couldn't go in the other direction too. All a matter of cost.

ok thanks guys...so to replicate that rez..i need to get a 20 inch or so 4k or close monitor.

@manassehkatz-Moving2Codidact What I meant was that both Windows (and macOS) and the greater ecosystem of applications generally did not handle rendering DPIs other than 96dpi correctly: so UI element layout calculations would be all messed up. Things didn't improve until Vista. A well-built custom application (like avionics, of course) will be able to handle it, but you couldn't run MS Word or anything like that on it.


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What format is the output from a GA aircraft microphone? WAV? MP3? or some other format
I'm trying to develop a personal weather station observation to a voice output on Unicom when pilot activated.
To start, I need to know what format is in the output from a GA aircraft microphone?  WAV? MP3? or some other format.

Why do you need a microphone to transmit telemetry data from the ground? You should use your data to control a text-to-speech generator and modulate the transmitter. Note using Unicom for such application likely requires an authorization.

I want to broadcast weather data over Unicom through a handheld aircraft radio on pilot controlled input.  This is currently being done commercially but you have to buy the complete system, sensors and all at a very significant price.  The TTS portion has several solutions available with several output forms, i.e. WAV, MP3, etc.

I see, this is possible of course. You have to use the raw analog audio frequency output which might be labeled HP or SP if there is an integrated audio amplifier. Codec outputs like wav or mp3 are not made for this. However you need to convert the impedance of the analog output (possibly 8 $\small \Omega$) in order to meet the one of a mike input (more about 200 $\small \Omega$ to 10k $\small \Omega$), else you'll experience a huge distortion or a tiny voice. You may want to ask how to do on the radioamateur Q/A site, this is one of their topics.

So the sensor data is sent to Google Docs, then run through TTS then to the transmitter.  When the pilot calls Unicom, the current weather observation is transmitted back to the pilot.

I cannot comment further without elements (e.g. do you use a MCU), and anyway this is not the place, still the principle is to convert sensors data to text (whether you need a txt file or can use a live ascii/unicode serial stream depends on your TTS board), feed TTS with text, convert TTS audio output to the correct impedance and send the corrected audio to the mike input of the transceiver. How the transmission process is triggered by the pilot is another part (ham repeaters have remote control by tone to kill uplink squelch, this is not different). This looks like an interesting project.

What problem are you trying to solve?  There are already automated WX broadcasts available, how is what you are attempting different?

I'm trying to get a specific station data out to the pilots going to that specific airport.  Interestingly, there is already an automated station 5 miles away but the winds are consistently different between the two stations.  That system costs 250k with 10k per year maintenance/calibration, much beyond out financial capability.

Google 'private awos' to get links to systems that do this. Budget ones are less than $10k.

Analog............................

Sound is ultimately analog. The waves of compressed and rarefied air molecules represent an analog signal. A microphone converts differences in air pressure into an analog electrical signal; a speaker converts an analog electrical signal into differences in air pressure.
How that electrical signal is processed between the microphone and the speaker is a design choice; you can use an ADC to convert the signal into a digital format for processing and storage before using a DAC to convert it back into an analog signal for transmittal. Or you can process and store the analog signal without ever converting it to digital.
If you do use a digital format, you must consider tradeoffs, such as: which format uses more or less storage space, which format is easier for your software stack to process, whether a format stores enough information to avoid introducing artifacts in the signal, etc. But as long as you convert the digital format to an analog signal, your transmitter equipment will not care about the format you used.

The output of a GA microphone is an analog signal consisting of a very rapidly varying AC voltage, in the range of ~tens of millivolts to hundreds of millivolts depending on the type of microphone.

Assuming it would be a digital microphone, the output is likely to be raw PCM (pulse code modulation), or sometimes MP3 or AAC. But the list of common headset connectors as used in aviation appears listing connectors for the analog signal.


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ADS-B for satellite Tx in Canada
Can simple rod transponder antennas be used to satisfy the Canadian requirements for a top antenna to communicate with ADS-B satellites?  (eg. RAMI AV-22)


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what speed was the "negative 4G inverted dive" in Top Gun
I realise that the "negative 4G inverted dive" described in Top Gun is a hypothetical manoeuvre, but I was wondering what sort of speed they would be flying at. I'm guessing low subsonic Mach 0.3, but I have no idea really. I guess the 4G force, depends on radius of the vertical loop and the speed, so different radii would give different speeds. The aircraft were theoretically an F-14 Tomcat (top) and F-5 Tiger (below). I am interested in doing some CFD analysis of the 2 aircraft in close proximity, so it would be useful to have a rough estimated of the flight speed. Thanks.

I think you're likely referring to "Top Gun: Maverick"; if so, you may want to edit your question to specify that movie.

No, this is clearly about the original Top Gun movie, not Maverick.

The maneuver described is so non-sensical that I don't think knowing an airspeed range would help.  In fact I don't think you could properly model it at all...
Start by asking yourself what the words "negative 4G inverted dive" actually mean, compare them to the movie footage of the alleged event, and then ask yourself some questions about what the aircraft was actually doing.
For example:

If you were inverted and pushing negative 4Gs, would you be in a dive?
If you were inverted, canopy to canopy with another aircraft that was upright, (as depicted in the scene) and the other plane was pushing negative 4Gs in a dive, would your G loading be positive or negative?
Starting from level, upright or inverted, if you entered a dive at 4Gs, how long might you be able to sustain 4Gs before it becomes an "Split-S"?
How much might your airspeed change during such a maneuver, and how would that affect your calculations?

And then look at the (phony) footage - what are they actually doing?  Really just flying along in close formation, canopy to canopy.  Maverick is inverted, but it doesn't look like they are pulling any Gs at all really, certainly the maneuver is gentle enough to leisurely snap a photo.
Even if the dive wasn't intended to be shown in the movie and happened just after Goose took the photo, Maverick's description of the event doesn't even make sense to me.  My advice would be to not waste any time trying to reconcile these Hollywood anomalies with reality.
But, if the airspeed parameter is the only thing holding you back from doing something you find interesting, I would suggest you start the maneuver at around 300KIAS, and presume that by the time the plane reaches 90 degrees nose down, they would be going at least 500.
P.S.  If you need any help answering the bulleted questions above please mention it in the comments.


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Thrust produced by a Lycoming O-360
How would I determine the thrust produced by a Lycoming O-360? I have looked for conversions of horsepower to pounds of thrust but have not had any success.

At what airspeed?

Can you tell us more about what you need this for?  Do you need a detailed model of thrust as it varies with throttle setting, altitude, and airspeed?  Do you just need to know the maximum thrust available?  Is the engine driving a fixed pitch or constant speed prop in this case?  Do you care about fuel consumption at all?

You have to know the details of the propeller. The value for static thrust is typically 4-4.5 lb/hp. An O-360 with a fixed pitch prop is somewhere around 700lbs static. Maybe with a CS prop, with blade pitch optimized, 750-800lbs.

Please consider the following: https://aviation.stackexchange.com/a/81009/7532 https://aviation.stackexchange.com/a/101652/7532 https://aviation.stackexchange.com/a/101679/7532 https://aviation.stackexchange.com/a/101657/7532 https://aviation.stackexchange.com/a/101650/7532

Welcome to the club.  Unfortunately, in aviation, some people are loathe to describe engine/prop output by thrust because prop efficiency, especially fixed pitch, will change with airspeed.
Generally, a fixed pitch prop is designed as a "climb prop" or a "cruise
prop", with finer or coarser prop pitch, respectively.
Props generate thrust by mass acceleration as spinning airfoils, so angle of attack of the prop is critical.
What one can do is build a "thrust curve" at various speeds (a power curve if you will), by first determining the thrust requirement in level flight at various airspeed with gliding tests.
Now you see how much excess thrust  (at full power) you have by climbing at those airspeeds.

level flight thrust + climbing thrust = total thrust

The level flight thrust is determined by sine glide angle × weight.
The climbing thrust is determined by sine climb angle × weight.
This method will give, to an approximation, the thrust output of the engine/prop combination at various airspeeds.

A reciprocating engine generates a power on its shaft which is measured in horsepower or Watt. That's all a reciprocating engine can do. What happens with this power depends on what is attached to the shaft.
If you attach a millstone to it then you're going to get some tons of flour per hour.
If you attach four wheels to it then you're going to get a car bringing around a couple of passengers and suitcases at some km/h.
And if you attach a propeller to it then you're going to get some thrust measured in lb or Newton. A quick and dirty estimation of the thrust produced by this propeller given the engine power can be found here.

You have to include a propeller efficiency factor in front of the cube root no or is that what k is for? In this video, a Cont C-85 with a fixed pitch prop produced about 320+ lbs of actual measured static thrust. The engine would've been well below its power peak tho, so probably only about 70-80 hp until it gets rolling.  https://www.youtube.com/watch?v=i_tX-U_GbI0

@usual impolite downvoter: explain your doubts so that I can improve my answer, thanks

Your answers get downvoted because they've little value, show little consideration for the question being asked.  People are not interested in answers that promote other related answers, or another answer that seemingly answers the question, all written by you.  Add value to se-aviation with answers that inform, rather than answers that provide. Teach what is going on here, power plant to thrust, show some interpersonal skills, & consideration for the poster. Such answers may take hours to craft & compose... Integrate references to other answers appropriately. We value your knowledge!

@ThomasPerry: seriously? I explained that an engine supplies power, not thrust. I explained that you have to attach a propeller to the engine in order to convert that power into thrust. I explained how to estimate that thrust from the power... Sorry but I can't do more than this. If you're so sure that my answer is garbage then just flag it and I'll delete it...

Seriously!  Do not delete your answer. I edited your answer, with all due respect to you, to informatively direct the answer to the question being asked.  If you find the edit acceptable, then let it stand, or if you wish, edit the answer otherwise.


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How is the memory system configured in avionics computers?
In common memory systems determinism is never achived, meaning that you do not know exactly when are you going to obtain the wanted data, as there can be Cache misses that slow down the data supply. In avionics, determinism must be guaranteed, at least knowing the maximum delay.
Do avionics computers assure no uncertainty, or do they have different memory systems?

I would imagine that the hardware configurations are much like those of any real-time system where errors, delays, etc. are not tolerable. Things like cars, rockets, CNC, etc. all need to have the data now and the hardware is designed to ensure that happens. I don't know exactly how those designs differ from your off-the-shelf home computer, but that might give you more to search on.

There's an easy way to prevent the unpredictability of cache misses: turn off the cache.

A far bigger issue then precise memory timing - which can actually be predicted quite well - is the overall system timing. See Apollo 11 for an example of when this wasn't handle well due to software issues and hardware limitations. The key in general is use a real-time operating system. That can be certain variants of the Linux family, but not your ordinary off-the-shelf workstation or server Linux and definitely not ordinary Windows.

Maybe having a look in the documentation of VxWorks might help

Determinism is out the window the moment you use DRAM due to refresh cycles.

I haven’t designed an avionics computer myself but have worked on many real-time systems.  Essentially the key is to work out the worst-case timings and make sure that the system remains within spec under these conditions.  In the specific case if a cache miss, the worst-case timing is still deterministic because we know how long it will take to identify a cache miss and then how long it will take to perform a read from non-cached memory.  As an aside, since we’re only interested in making sure that worst-case is within spec, there’s not so much incentive to optimise the best-case, so as Jörg has suggested, turning off cache isn’t necessarily a bad idea if it removes other uncertainties.

As you say, there is not much incentive to optimise the best case. But there is incentive to optimise the worst case. And turning off caching does exactly do that

@DeltaLima Turning off cache downgrades the best case to the worst case. It does not change the worst case.

@user71659 It does improve the worst case. With the cache, the worst case is  something like this: 1) search data in cache find out it isn't there 2) load data from slower storage 3) safe data in cache, 4) return data. Without the cache, step 1) and 3) are not there, and thus a) the performance of the worst case is improved, b) the best case is equal to the worst case and so the variation in timing is gone. Both are good things in many real time applications.


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What is the speed the fan blade would go if it would separate from the shaft with the engine at full throttle?
I'm making a simulation of a blade separating from the shaft to test the case of the engine, but i don't know what speed should i put on the blade to go outwards the case, anyone has any idea how to measure this? thank you

Not an answer to your question, but just FYI this is an extremely challenging type of simulation.  What level of accuracy are you looking for here?  For modern carbon fiber composite cases, to get the same level of accuracy as the OEM simulation, I would expect you need a team of many people working for several years, as well as significant experimental material property measurements. This paper gives an idea of the complexities involved: https://ascelibrary.org/doi/abs/10.1061/(ASCE)0893-1321(2009)22:3(260)

@DanielK: This document is behind a paywall, but this similar one isn't: Developing an Efficient FEM Structural Simulation of a Fan Blade Off test in a Turbofan jet engine

There is no simple answer to this question, but you can take a mean value of 300 m/s as Nasa does in this article.
The tip of a fan blade has a linear velocity of more than the speed of the sound for a modern engine (e.g. 420 m/s). The root of the blade is a much modest velocity as the diameter of its path around the shaft is small. So the tip and the root won't have the same velocity when the blade departs from the fan disk.

Source
You can compute the actual velocity at any point of the blade, it's the product of the perimeter of the point path and the rpm: $v = \pi d * rpm / 60$, in m/s if the distance d is in m.
What counts now is how is the blade mass distributed between these two ends. A fan blade has a large part of its mass in the outer half. This mass will pull the other half. As the blade is rigid, velocities will equalize at a mean value, and at the same time the blade will rotate around it's center of gravity.
See Containing a blade-out


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ADS-B UAT message structure
I have found extense information regarding the 1090ES message structure. However, I have not found reliable information as for the UAT message structure, which surely differs from the 1090ES one.

I feel like this question is a bit broad, without fully understanding the details of the subject. Perhaps this answers your question (perhaps it's a duplicate): https://aviation.stackexchange.com/questions/29771/what-is-the-difference-between-ads-b-uat-and-ads-b-es

You should post what you think you know, with references, so people don't have to recreate/guess. That also provides clarification as to what you are asking.

The UAT frame is officially described in ICAO Doc 9861 Manual on the Universal Access Transceiver. It differs from the DF17 messages used by ADS-B using the 1090ES layer of a mode S transponder. For the later you see see this question.
The UAT frame has an ADS-B segment which can contain an ADS-B Message Data Block (MDB). Note the UAT frame is used both by aircraft and ground stations. Ground stations can upload ADS-B data about aircraft they track (TIS-B service). The following describes first the data block sent by aircraft. The MDB is organized into elements.

The MDB actual content is determined by its header containing:

A type code. There are several types.
The address qualifier which tells how the aircraft address is to be understood: A 24-bit ICAO address or an anonymous address when the message comes from an aircraft, or a pseudo-address (trackfile ID) when the message comes from a TIS-B ground station which cannot identify the aircraft by an individual address when the aircraft doesn't broadcast in mode S.

The MDB contains first:

A 24-bit ICAO address on 3 bytes

A state vector on 13 bytes:

A mode status on 12 bytes:

It can also contain other elements:

An auxiliary state vector on 5 bytes, for some block types (altitude from a second source).
A target state on 4 bytes, describing where the aircraft is aiming to.
Two trajectory changes on 12 bytes each.

Regarding the pseudorandom addresses which can be used to relate the block to an aircraft, you can read What's the differences and the risk of duplicates, between ADS-B and TIS-B addresses? (inc. ICAO and self-assigned options).
If you need more information on a specific element I can include more details in this answer, but obviously not all elements can be detailed, the specs are 70 pages long.


text:
I currently have L2 visa , am I eligible to complete my CPL program in USA
I am from India, I currently hold dependent L2 visa , can I complete CPL program (commerical pilot licence) in USA

I think this is a better question for Law SE.  Specifically immigration law.  (AFAIK visas for training and education are not aviation specific)


text:
When discussing a “feathering, counterweighted propeller” where are the counterweights?
We are learning about propellers in school. To my understanding, generally a non-feathering, non counterweighted prop uses centrifugal twisting moments to lower blade pitch while oil pressure is used to increase.
This is flipped with counterweighted props right? We use the centrifugal force of the counterweights to increase angle, while oil decreases it?. But, where in the world are these counterweights? None of my books or any google searches tells me much.

They're at the blade roots. If the propeller has a spinner, they are usually hidden, but if there is no spinner, they stick out like sore thumbs. Oil drives the blades fine, the weights drive them coarse, and if the prop is feathering, and the feathered position being beyond coarse, there will also be an internal spring to drive the blades all the way to feather in case the rotational speed isn't enough for the counter weights to do the job.
On a feathering counterweight prop there are also centrifugal pitch stops inside the hub that limit the prop to normal coarse pitch until the RPM is above 500-800 rpm, when they move out of the way to allow the blades to feather if the engine fails while making power. The stops keep the blades at coarse pitch when you shut down normally. When the engine is making power, all you have to do is dump the oil pressure and the prop will feather by the weights, helped by the feathering spring.


text:
Why don't we treat all takeoffs as short field in GA?
Depending on the airframe, there are a number of techniques to reduce the Take Off Distance required. For example, deploying flaps.
What advantage is there to NOT using short field take offs, even when runway length is sufficient? Surely it's always advantageous to require the minimal amount of runway, thereby adding a larger margin for error?

In my opinion –and that's why this is a comment and not an answer– if you have a long and smooth runway, it's better to take off in a sedate way, using little or no flaps... Short-field techniques should be reserved for short/rough runways.

Best rate of climb vs best angle of climb

Short-field take-off techniques often achieve a shorter ground run by hurting climb performance. While having more runway is great for safety, planning to use less of the runway is not a huge benefit: you always plan to have enough runway left if you need to abort during the take-off roll. It's much better to have more height quickly in the climb-out: it gives you more margin against obstacles after the runway's protected area, and it gives you more height to land in case of an engine failure after take-off (EFATO).
The numbers for a normal take-off optimise for a good rate of climb, which has the greatest benefit to safety. A short-field take-off gives you an extra option when the runway length is too short for that - at the cost of some margin if there's a problem in the climb-out.

Technically, climbing at Vx (best angle) is better for obstacle clearance than a normal Vy (best rate) climb, though, right? Vy does gain altitude faster per unit time, but doesn't gain altitude as quickly per unit horizontal distance (because the speed over ground is slower.)

First off as the pilot in command, you are free to do this if you feel it is the safe way to operate the aircraft in a given situation even if runway does not dictate it.
According to the FAA's handbook the short field take off requires a high degree of control of the aircraft,

The pilot should be aware that, in some airplanes, a deviation of 5
  knots from the recommended speed may result in a significant reduction
  in climb performance; therefore, the pilot must maintain precise
  control of the airspeed to ensure the maneuver is executed safely and
  successfully.

While an experienced pilot may be ok with this student pilots and newly minted ticket holders may feel less comfortable and thus choose to only fly from runways where this is not required, although it should be noted this is part of the ACS and thus part of getting at least a PPL here in the US. Due to the degree of precision the maneuver may be used less than a standard takeoff.
There is an interesting article here worth reading on the topic.

As Dave and others have already mentioned, short-field takeoffs result in taking off with significantly less airspeed than usual. Your goal in a short-field takeoff is essentially to fly the plane just slightly above the point where it is not flyable. As a result of this, the margin for error in a short-field takeoff is considerably smaller than in a normal takeoff. In addition to the relatively poor climb-out performance mentioned in Dan's answer, you're intentionally trying to fly just beyond stall speed. Relatively small wind gusts can put you back on the ground in a hurry, as could momentarily pitching up too much.
All-in-all the short-field takeoff is just a relatively more dangerous way to take off if you have sufficient runway for a normal takeoff.

You'll have less control authority and, so, less ability to correct the plane's attitude in gusty conditions.
You'll have less airspeed and be more susceptible to stalling at low altitude (whether due to gusty winds, accidental excess pitch, or a combination of the two.)
You'll also be less able to climb clear of obstacles at the end of the runway.
The flaps will also be providing additional drag, so you'll use up more horizontal distance in order to get up to speed for the climb-out.

Your only real gain for all of these trade-offs is that the wheels will have a shorter roll across the ground, so it's just not worth it unless you really don't have the runway to spare.

re: clearing obstacles: so the overall higher drag from being in the air with flaps is worse than from rolling down the runway for longer, and lifting off closer to whatever obstacle?  I guess that makes sense, because you're getting the lift for nearly free when it's coming from contact force of your tires (with your wings nearly horizontal), vs. from pushing on air at a higher angle of attack.  So even though you get into the air sooner, you still have less height at the far end of the runway.

@PeterCordes Correct. When rolling across the ground with 0-10 degrees of flaps, your engine power is going mainly toward forward acceleration of the aircraft (granted, the tire contact with pavement does add some drag, but not as much as actually flying, let alone with full flaps at low airspeed.) When doing a short-field takeoff, the extra flaps are creating extra drag, which some of your thrust must counter and, once you get airborne, you're using a lot of your thrust to counter drag in order to be able to fly.

@PeterCordes That's an interesting point, about the lift from the tires!

Short field takeoffs are more complicated than simple takeoffs. That is why they are taught later, once you are familiar with normal takeoffs.
Depending upon the plane, there are several steps you need to take for a short field takeoff:  add flaps, line up before the piano, press brakes, full power, check engine gauges, release brakes, etc.
This is simply more complicated than full throttle/check engine gauges. There are a thousand things that you need to keep in mind while flying. It is best to keep simple things simple. Of course you can always do short field takeoffs if it pleases you. Most runways you will takeoff from will be long enough from a GA perspective. In case the runway is short, you should of course use the short field technique. :)

There’s an argument to be had for standardising towards a common procedure though. Arguably, it is more likely the short field takeoff will be carried out below required standards when it matters most if the procedure is rarely used. Of course, as stated in another answer, the potential decrease in climbout performance should be balanced against that.

@Cpt Reynolds:  Common procedure would be good if all runways (and other surfaces one might wish to take off from) were identical.  But brakes & full power are not a good thing to do on a grass or dirt strip.

I used to fly a 4-seater Rallye Minerva, and, if I recall correctly, the recommended
short field take off involved putting on full flaps (30°) just before liftoff
speed (the flaps were operated by a handbrake sort of affair) and then basically flying level until an appropriate speed was attained.
While no takeoff was relaxing, this procedure was a little unnerving (it took
quite a bit of effort to latch the flaps in, and there wasn't always a second
chance), and certainly not one I would use on a regular basis. A crosswind added to
the tension as the liftoff speed was fairly slow (something like 42KT).
This was a lot more work than I would want to do when operating from a busy
airport, and generally reserved for shorter 'fields' (100m, yep, you read that
right).

I would say it all depends on the aircraft and its POH and also the runway itself (soft or hard). For instance, in the Cessna 150/152 (and I believe 172), the short field takeoff (with obstacles) requires no flaps, so there wouldn't be any penalty for the climb rate and would always be advantageous unless on a soft field. If there is no obstacle, 10 degrees of flaps would get you off the ground quicker and give you if I recall correctly a 10% penalty on the climb rate, which could be a good trade. But some aircraft requires more flaps, or the penalty on the climb rate is higher than others.

Furthermore, you want to minimize the time of full power to the engine to reduce the chance of its failing. You also want to keep fuel burn down so there's more reserve at the end - or less to be loaded to start, allowing more payload.
A "normal" takeoff improves all the above along with airspeed margins, visibility over the cowling, cooling airflow to the engine and more. All of which are benefits it offers compared to a short (or soft) field takeoff.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Can you identify this scrap cockpit section I found in a scrapyard?
I recently found a scrap cockpit in a scrap yard, and I'm hoping there's enough remaining to identify the aircraft type from pictures.
Unfortunately, all are taken through fencing as I don't have access to the compound.
Imgur Link

it reminds me of an A320. Though what such a "new" type would be doing in a scrapyard I don't know.

Going by the cockpit glazing, I'd say that's a Hawker Siddeley HS.748:

Wow, that looks like a fantastic bet. I'm trying to see if I can find some good cockpit shots but I very much suspect you're correct

Aaand here we go - positive ID on the little wheel (Rudder trim?) on the back of the center console: https://cdn.airplane-pictures.net/images/uploaded-images/2012/4/18/204161.jpg
Fantastic work, Hobbes!

The small eyebrow window is a clear hint. +1

I wonder what the line of thought was behind that eyebrow window's particular shape.  I bet there was a specific reason for it.

@PeterKämpf What is that window for please?

My guess regarding the small window - https://live.staticflickr.com/4479/37469435842_8122885bd1_n.jpg ;)

@Cloud: For observing traffic in a turn. See here for the same thing on old B737s.


text:
Why don't passenger aircraft use the trijet configuration anymore?
As a kid I distinctly remember seeing aircraft like the bright blue KLM MD-11 having the prominent third engine on the tail.

https://commons.wikimedia.org/wiki/File:KLM_MD_11_AMS.jpg
However, I don't think I've seen a plane in the past few years (besides maybe a few smaller private jets) that has a engine on the tail - let alone a trijet configuration.
What's with their disappearance?

Related: Why does the 747 have 4 engines instead of 2?

FedEx currently flies at least one trijet, as I see it on approach most days about 5 pm.  Quite large, maybe an MD-11?

@jamesqf: And I went by a FedEx DC-10-10 just this past winter while flying to see family in Massachusetts and back for the holidays...

@Sean: I haven't noticed that particular FedEx plane in a while, though, so maybe the question was just a bit prescient :-)

@jamesqf FedEx and UPS bought up all the trijets that the airlines dumped. Since their planes are parked all but a few hours per day, low acquisition cost matters more than high operating cost.

The fewer engines an aircraft has, the lower are its operating cost. Engines are the most maintenance-intensive part of an aircraft, and doing a hot section inspection on two large engines costs less than doing it on three somewhat smaller engines.
When the tri-jets were developed, no sufficiently large and powerful engines were available. They were already cheaper to operate than the four-engined aircraft, and too large to have sufficient power with just two. Now, with engines which can deliver a static thrust of more than 100,000 pounds, everything below a Jumbo Jet or an A380 can be powered with just two engines.
Another reason is increased engine reliability: With three or four engines, an engine failure is less of a problem than with just two engines per airplane. Previously, route planning had to keep a maximum distance of 60 flight minutes to a diversion airport. In 1964, this was waived for three-engined aircraft, but twins were still bound to this restriction. With more experience and better engines, this rule has been relaxed for twins gradually to 120 (1985), then 180 (1988), and now 370 (2014) minutes for the Airbus A350 XWB, and twins have become much more versatile for their airlines.
Some of the old tri-jet designs were quite popular with operators: The last Tupolev Tu-154 was built only in 2013. But besides the Dassault Falcon 900 and 7X business jets, I don't know of any trijet which is still in production.

Interesting! I'm curious if we'll ever move to single engine passenger aircaft.

I think its unlikely we'll ever see single engine passenger jets. You always need redundancy. Anecdote: They call the engine on single engine aircraft "Air conditioners" - when they stop working watch the pilot start to sweat!

@Jamiec: Some do, but not the bigger ones.

But that's not a jet. Are there any single engined jet aircraft that i've somehow missed?

@Jamiec: If you restrict it to jets, you win. Private and business jets don't count.

Worth mentioning #2 manufacturing (and maintainance - already mentionned) complexity/costs, the larger fan diameter, structural problems (fragile=>strengthened=>heavy), aerodynamic problems mounting an engine on the tail, and the risks it implies in case of a mechanical failure or fire (engine in the middle of critical components of the plane)

You brought up a point in your last paragraph that I was thinking of while reading the rest of your answer.  The 7X is a recent clean-sheet design, yet they still went with a three engine design so there must still be some benefits to it.  Any idea why they would go that route in spite of the disadvantages that you list here?

@Jamiec Actually, the Caravan is technically a jet. It's a turboprop. For larger transport-category aircraft, I don't think it would even be legal to make a single-engine one. It's rather difficult to continue a takeoff and climb out after a single engine failure when you only have one engine to start with.

so on a large 2 engine aircraft, it can fly for up to 4 hours on a single engine without serious issues?

Another minus-point for new designs is that you inevitably need different mounting systems, nacelles, thrust reversers, etc, etc, for the wing and tail engine positions. More common parts = less inventory needed for spares and maintenance = cheaper both to build and to operate.

The Falcon 7X has three tail-mounted engines which is one way to overcome the common-parts issues, but that idea doesn't work well for bigger engines.The PW307s are only 6,400lb thrust, not 100,000lb.

Bizjets and airliners doesn't share the same market, and doesn't share the same requirements. 3 engines on a bizjet means less thrust/rpm per engine that can produce less overall noise signature, meaning much more airports to serve, while still powerfull enough to take of from small airfields even with one engine failure after v1. The 7X, especially, were designed with the developement of larger or heavier versions in mind.

@Lnafziger: I don't know the details, but I would expect Dassault knew their way around a trijet and developing a different configuration would have cost more. Also, business jets follow a different logic (or the Piaggio Avanti would be more successful). In the peeing contest of how many engines your jet has, the 7X owner has a clear advantage. Maybe Lockheed should take up JetStar production again.

@user1663987  Any twin engine plane needs to be able to fly on only 1 engine.  Since the current generation of large passenger jets have glide ratios of ~20:1, being more than ~15 minutes from an airport means that permanent loss of all engines would result in a crash.  What's changed over the last few decades is that jet engines have gotten more reliable; making the random loss of two in a short period of time sufficiently less likely that the distance from an airport could be increased without an unacceptable level of risk being taken.

@PeterKämpf Well, they also make very successful two engine jets as well, but there are performance benefits that a three engine design has (as KarlStephen mentioned in his comment, losing 1 engine on takeoff has less of an impact if you are starting with three instead of two...)

Twins fly cross Atlantic....that's more than 240 minutes from an airport...

@andrewmh20 You're never more than 240 minutes from an airport on a northern Atlantic route. The flight time from Shannon (Ireland) to Halifax (Canada) is only about 330 minutes, so when you're halfway you're 165 minutes from either airport. The other way is faster. And that's not counting Reykjavik, which is conveniently situated in the middle of the Atlantic.

@MikeScott: It would be even more convenient if it weren't so darn far north...

@reirab: The Caravan is a turbine-powered aircraft.  It is not a jet.

@mikescott the 330 minutes flight time is two engine speed. ETOPS time is one engine inoperation speed. So at half way you will be more than 165 minutes from either end if one engine fail. You will be forever away if both engines fail.

The main reason for selecting three engines was reliability issues with gas turbine engines used in the dawn of the jet age. The FAA Operating Requirements §121.161 Airplane limitations: Type of route says,

... no certificate holder may operate a turbine-engine-powered airplane over a route that contains a point—
(1) Farther than a flying time from an Adequate Airport (at a one-engine-inoperative cruise speed under standard conditions in still air) of 60 minutes for a two-engine airplane or 180 minutes for a passenger-carrying airplane with more than two engines

Most of the initial tri-jets were configured for long range operations as twin engined aircraft could not be operated in most transatlantic routes.
However, as the engine reliability has improved, the regulatory authorities have certified a number of twin engined aircraft for ETOPS (Extended Range Twin Engined Operations). As airlines prefer as few engines as possible (which translates into lower upfront and operating costs), tri-jets have become a relic of the past.
Maintaining the third engine on top of the fuselage is a major headache compared to the other two. Also, the placing the third engine has been a design trade-off between aerodynamic efficiency on the one hand and easier installation (and lesser cost) on the other hand.
For the same reasons, we are not seeing any four engined aircraft and every aircraft under development is twin-engined. Also, improvements in engine power (777's GE-90 produces nearly twice the thrust of MD-11's GE CF-6) and fuel economy (today's aircraft burn around 10% less fuel compared to the aircraft from 1980s) mean that the necessary thrust (and range) can be generated by lesser number of engines.
Another (minor) point is that the bypass ratios have increased in the recent decades and this might present difficulties in placement of the center engine.

+1 for mentioning both maintainance complexity of the #2 engine, and the high bypass nightmare.

I don't know about the airliners, but the third engine on the Falcon business jets are actually in line with the two fuselage mounted engines (and they use the same S-duct technology that was licensed from Boeing so I assume that it is similar) and are maintained not from above, but from below just like the other two.

Other (great) answers have already covered most reasons.
On Business Jets side, you can do this : http://www.airteamimages.com/dassault-falcon-7x_CS-DTS_masterjet_176224.html
But not that often with airliners. :P
Well, joking put aside...
Cost:
A third (or second) engine on/below the tail adds specific parts/components, that have to be manufactured, maintained, and spare parts have to be made available for the entire lifetime of the type. Just like the reason why "eyebrows" were removed from the 737 line, and not a single airliner has purchased the 777 with folding wings (and the idea dropped on A380-like projects), reducing costs is a relevant reason to not manufacture "special" parts whenever possible. Best sellers are aircraft that are cheap to handle and maintain. If you can use larger engines to get two instead of three, then...
Similar reasons for unmounting the #2 engine. On a relatively small jet, you can unmount the engine just like it was on the Boeing 727. However, to make that possible with engines the class (and size) of a GE90, you need strengthened structures (increased weight: bad!) around the tail cone, special lifters, a tail cone large enough to contain that engine, compliant with regulation in case of a fan blade failure. Hydraulics and other electrical wiring must be secured. That adds many more special components that have to be checked for airworthiness on a regular basis. When your aircraft is stuck at an airport without the appropriate equipment, you must ferry them there, with the replacement engine. Cost!
It's highly unlikely we'll see a tail mounted engine on airliners the size of a 777 in the future.
Noises and vibrations:
Small engines are OK. Large engines not that much. Even with the incredible progress we have made in reducing engine noise, vibrations are still a major factor, and engine pylons are the best way we have to reduce them. A tail mounted engine doesn't really have a pylon.
Aerodynamics:
Brutally pitching up the aircraft can reduce or disturb the #2 engine intake airflow, with sometimes noticeable issues. This is a major concern for pilots operating on hot and high conditions. This also happens during stall and deep stall. Tail mounted engines requires larger or extra tail surfaces to stabilize the aircraft and reduce drag (weight + more parts to maintain)
Aircraft behaviour:
When the engines are not mounted in line with the other two (DC10/MD11, Tristar), the center engine produces some specific pitching behaviours depending on loading, thrust and flight phases. It's worse in the case of one inoperative engine. While this behaviour has saved the life of many in the past, it was also a factor in some crashes or close calls.
Related: aircraft behaviour varies greatly between a short version of the frame to a longer one. Stretching a three engined aircraft requires much more research, development and testing than a twin engine one. Having optimized types meeting airlines requirements in your catalog is not that easy with three engined aircraft.
Safety concerns:
In the case of a component failing at a high rotation speed, a fuel leak, or a fire, mounting the engine in the fuselage is obviously not the most seducing option. The not so distant Qantas A380, Air Transat A330, Concorde in Gonnesse... Fighting a fire on the engine #2 of a Tristar is not the same as fighting the fire on the BA 777 at Las Vegas.
You can't conduct a fan blade overview upon walk around on engine #2.
Reengining:
You can create new nacelles for more powerful, quieter and more fuel saving engines for a 737 (100/200 > Classics > NG > Max > ...) or an A32x (Neo), avoiding the need to develop an entirely new air frame. Reengining the 727 had mitigated results. All KC135 have been reengined and the 747 with the 8I/F. A330 and 777s... Going from the DC10 to the final version of the MD11 (which is basically a reengined and stretched DC10) wasn't that easy. Many retrofits were made available several years after the MD11 entered commercial service. As we don't clearly know what the future is made of, a three engined aircraft may fail to comply with future technologies, which disallows lengthening the lifetime of the type, unless designed from the start to be upgraded, like the Falcon 7X (larger/heavier versions in the plans).

However, having three engines is not a bad thing. It all depends on the purpose of the aircraft. One extra engine can reduce take off roll, allow the selection of smaller and quieter engines (in some rare cases), increase ETOPS certification, give access to hot and high airports, etc. If those reasons are relevant enough to cancel the extra cost required by the extra engine, then you can manufacture a three engined aircraft (or a six engined, like the An225).

I assume the pitching the aircraft up would disrupt air flow to engine 2 because of the massive body in the way?

+1 for pointing out the weight disadvantage of rear mounted engines.

@codedude: Sorry, I missed your question. That's more or less that but you're correct. Aerodynamics (fluid flow) is a complex science (I don't master at all) Not only the body interferes, but also the wings (root) and whatever shape in the way. Plus, wind direction and gusts matter (not always facing aircraft), but we'll end with an even longer answer. Brutal pitching are rare, but do happens from time to time. Pilots are well trained on the type they're qualified to handle them at critical phases like take off and landing. (Thanks FreeMan for the edit -english is my third tongue)

No problem, Karl. Your English is better than many American's for whom it's an only language.

First of all, the L-1011 had a fourth hydraulic system compared to the DC-10/MD-11 which only had three.
Secondly, the L-1011 was a fantastic aircraft which had design input from Kelly Johnson, the man who brought us the SR 71 Blackbird and the F-104 Star Fighter.
The L-1011 was by far the superior aircraft and had capabilities that have since only been met for an aircraft of its size by the 777. It could even land itself.
What hurt the L-1011 was the financial failure of Rolls Royce that delayed the aircraft's entry into the market by a year. It never recovered from the orders lost to the DC-10 by AA and United who were desperate to get a tri-jet into their fleets.
The engines couldn't be changed because the Rolls Royce RB-211 was specifically designed for the L-1011's center engine housing and nothing else would fit, and there wasn't time for a redesign, retest, and re-certification. Fortunately the British government bailed out Rolls Royce so that the engines were eventually built and delivered.
The final straw for the DC-10 was the crash in Chicago, though technically an AA maintenance failure, the DC-10 was poorly designed and rushed into the marketplace to take advantage of the L-1011's delay. Not another DC-10 was ordered after that incident, and the MD-11 was simply a repackaged version of the same problem aircraft, made of composite materials and more fuel efficient or so everyone thought until it went into service. Another white elephant.
Standard on the Tri-Star was a co-pilot stick shaker, an extra cost option on the DC-10, as well as automatic electrical bus relays which transferred load from a dead engine to a live one, standard on the L-1011 and an option on DC-10, and finally the front slats on the L-10 mechanically locked into place once hydraulically extended, something not offered on the DC-10, which is why AA 191 crashed. Had this been an L-1011, that accident would not have occurred.
The final death knell for the Tri-Star was that Lockheed simply wanted out of the commercial aircraft marketplace so that it could focus on military contracts.
Boeing had no reason to offer a Tri-jet as it developed the long and short versions of the 747. In fact, the Tri-jets were a design competition between Douglas and Lockheed based on American Airlines criteria which initially ordered the L-10, but switched to the DC-10 after Rolls Royce went into bankruptcy.
As for the 727, never intended to be more than it was, an aircraft capable of short ETOPS, mostly to the Caribbean or Hawaii.
Ask any pilot who had flown both the Tri-Star and the DC-10 as to which he preferred and you'll find that almost all will pick the Lockheed.

Thanks for the additional info! I never knew about that about the DC-10s.

Actually, Boeing did consider making a trijet version of the 747, which would have used an S-duct (like the L-1011) and would have been designated as the 747-300 (no relation to the 747-300 that was actually built), but abandoned the concept without going past the drawing board.

Couldn't agree more on the differences between the TriStar and the DC-10. There is another difference: While the hydraulic lines on the DC-10 went through the rear pressure bulkhead all at the same spot (making the UA 232 accident possible), they were routed in the TriStar in three different places (left, right and bottom, which is standard for military designs).

The major reason for going away from trijet was a series of total hydraulic failures following an uncontained engine failure. This happened in both the L1011 and the MD-10 (but not the 727)
When an engine failed, high speed debris from the failed engine would cut the hydraulic system and control cables. The result was an airplane without conventional controls. For the most part the result was a total loss. In the case of the Souix City event, https://en.wikipedia.org/wiki/United_Airlines_Flight_232
four pilots were able to land the plane (almost) and the resulting crash only killed about 1/3 of the passengers.
Not a good idea, three engines.

Can you explain further what about how the engine in the tail is worse in this situation than the two on the wings?

In short, because the engine is embedded in the tail, a "blade-out" failure is going to damage the tail. Engines in nacelles have some built-in shock absorption inherent in the nacelle mounting, so first they're better able to contain debris because the nacelle can move to help the containment shroud "catch" the parts of the disintegrating turbine, and second when the nacelle moves it isn't overstressing the entire wing like a tail-mounted engine would stress the empennage.

Perhaps should deserve an upvote for the explanation, if it were to be included in the answer itself. A turbine desintegration is not a 0% chance (whatever the cause: metal fatigue, overheat, overspin, inhaled foreign debris..) Engines naceles mounted on pylons doesn't decrease risk of failure, but do decrease risk of hitting critical components like hydraulic pipes upon desintegration (surface probability, the farther the critical components...) It's also a better way to delay damages inflicted by sustained fire on an engine. However, those concerns were already raised above.

"The major reason for..." - unlikely ! Major concerns are those airlines have to handle on a daily basis : cost, reliability, and efficiency. See most upvoted answer. Turned in a crude way, airlines do care for safety, but not a the cost of mere gain, when competition is fierce. Otherwise, we would still have much more four engined aircraft around; even long range cargo has become twin engined. In a way, the tail mounted engines involved in disasters is just a contributing factor. We still have a lot of rear mounted engines near critical components that doesn't lead to that much crashes.

Several new supersonic transport (SST) planes in development are using a tri-jet configuration. In the previous generation of SST airplanes, such as the Concorde or the Tupolev Tu-144 required four engines. The new generation is pairing down by one or two engines for flight.

The Boom Overture will feature three Rolls-Royce/Snecma Olympus 593 engines. I assume because they could not get enough thrust from two engines and hit Mach 2.2. Another SST, the Spike S-512 is being developed with only two engines, but will have a maximum speed of Mach 1.8. The Overture is planning to enter service in 2029.
Other three-engine planes in development include The Sukhoi-Gulfstream S-21 (development has stalled) and the Aerion AS2.
I would agree with other answers regarding the simplicity of two-engine designs. I just wanted to share this to show three-engine planes are still being developed.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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What and when was the first gyroscopic flight instrument introduced?
One of things which consistently amazes me about flight is the exceptional progress in the early decades of flight - especially in terms of avionics. Wikipedia tells me that the first ILS landing was in 1938.
I'd like to understand more about the early development of gyroscopic flight instruments - in particular, what the first instruments like? When were they first put to use?

The gyrocompass invention has been claimed by Sperry and Anschütz-Kaempfe for the naval industry. In 1914 both tried to sold one to the German navy, Anschütz-Kaempfe sued Sperry. Einstein himself demonstrated to the German court that Anschütz-Kaempfe was right. Other litigations in the US and GB were lost. According to Wikipedia: "The first functional gyrocompass was patented in 1904 by German inventor Hermann Anschütz-Kaempfe"

It appears that the first gyroscopic flight instrument in aviation was a gyroscopic stabilizer, with the purpose of maintaining stability and control in a Curtiss C-2 biplane; it was first used (publicly) in 1914.
For this, the inventors, Elmer A and Lawrence B Sperry were awarded the Collier Trophy in 1914. Apparently they did this by,

...linking the control surfaces with three gyroscopes, allowing flight corrections to be introduced based on the angle of deviation between the flight direction and the original gyroscopic settings.

Lawrence Sperry and gyroscopic stabilizer, Image from wright-brothers.org
The device (with the gyroscopes spinning at 7000 rpm) was first tested by Lawrence Sperry and Berringer on a Curtiss F aircraft in 1913, with the first public flight in 1914.

Sperry’s second flyby in Paris in the 1914 competition, with Emil on the wing. Image from historicwings.com
Elmer went on to develop the turn and bank indicator and an optical drift indicator, for which he was awarded the Collier trophy again in 1916.

Wow, thanks for that - what incredible engineering


text:
How would I confirm the DC polarity of a 1960's Turn and Slip Indicator?
I have a 1960's gyroscopic turn indicator which I would like to power up. It has, what I presume to be, some kind of standard connector and the plate confirms 28 Volts DC.
The pins are labeled "A" and "B".
How would I confirm which way round the polarity is? Neither pin is connected to ground/the chassis.

Because the pins are probably simply connected to DC electric motor, likely neither polarity won't destroy the gyro and incorrect connection will then result in opposite indication. But of course, I can not know for sure if there is any mechanical or electrical detail which would cause (immediate) damage when reverse-powered.

I have found some schematics of new indicators which list pin A as positive and B as negative.....

If I were you I'd open it up and see how it's wired. That usually answers the question, but Martin is right, the polarity will likely make no difference if it's a DC instrument, other than the wrong one giving you the opposite indication of what is desired.


text:
Are TIBS and TWEB in Alaska discontinued?
My 2021 paper edition of FAR/AIM still mentions TIBS (7-1-8) as Alaska-Only, but when I look at the Alaska Chart Supplement I can't find any TIBS numbers.
https://aeronav.faa.gov/Upload_313-d/supplements/CS_AK_20211007.pdf
https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/dafd/

Yes TIBS and TWEB were discontinued in Alaska on January 1, 2020 according to the January/February 2020 edition of FAA Safety Briefing magazine and FAASTeam notice NOTC9903.

As part of FAA efforts to modernize and streamline service delivery, Flight Service will discontinue the Transcribed Weather Broadcast (TWEB) and Telephone Information Briefing Service (TIBS) in Alaska, effective January 1, 2020.

The TWEB is a continuous broadcast of aeronautical and meteorological information over a limited network of Very High Frequency Omni-Directional Range (VORs) and Non-Directional Beacons (NDBs) across Alaska.  A similar broadcast service, the Hazardous Inflight Weather Advisory Service, known as HIWAS, is being discontinued in the contiguous United States (CONUS).

TIBS is a continuous telephone recording of meteorological information that pilots can access without going through a Flight Service specialist. TIBS was discontinued in the CONUS in September 2018.

The July 16, 2020 revision of the AIM still mentioned TIBS and TWEB but those were removed from the AIM in the December 31, 2020 revision.

This change removes references to TIBS and TWEB as these services are no longer provided by Flight Service.

Your 2021 paper copy of the AIM was probably written using an older 2020 version of the AIM.

Welcome to Av.SE! Nice answer to a question nobody else has addressed.

@RalphJ Thank you!


text:
Did I identify these aircraft correctly?
I photographed a couple of aircraft and tried to identify them, but I'm not sure if it's correct. For me, all of them look like an Airbus A320, but I'm really unsure. So which of these aircraft is an Airbus A320 and if not, what's the correct type?
Airbus A320?

Airbus A320?

Airbus A320?

Airbus A320?

In all three cases, the aircraft's registration number is clearly visible. Google that and it'll tell you exactly what type of plane it is (e.g., the second picture, OE-LEL is an Airbus 320-214 with CFMI CFM56-5B4/3 engines, configured with 180 economy class seats, which first flew on 6th January 2006).

Also, it would be helpful if you could clarify your question to say what you were unsure about. Are you interested in, say, identifying an A320 vs a B737, or A320 vs A319/321? The current question (Is each of these four photographs an A320?) really isn't much use to anybody but you; a question more along the lines of "How can you identify between A319, A320 and A321?" would allow an expanded version of @MikeFoxtrot's answer, which would be useful to anyone who had seen one of these types of planes.

@DavidRicherby I think that learning to identify planes without searching the identification number is a good skill. So although this particular question may have been a little unclear, the actual category should not be discouraged, IMHO.

for this type of thing asking in chat would be better,

@flyingfisch I agree but that's where my second comment comes in. "Are these A320s?" is useful to nobody except the asker, because the answer to the literal question ("Yes, they're A320s") doesn't help anyone work out what's an A320 and what isn't.

Looks like it :)
Double window exits over the wings, so no A321 or A319 (with a few exceptions such as Easyjet's A319)

All correct.
When you look at the engines, you'll see that the British Airways A320 is equipped with different engines than the other three.
The Swiss and NIKI aircraft are A320-214 and use the CFM56 series engine build by CFM international.
The BA aircraft is an A320-232 and it has the IAE V2500 series engine build by International Aero Engines.


text:
Why Search for MH 370 in this area?

Consider the above figure:
Why the search is conducted to the red boxed area in the figure. while the actual route of Flight MH 370 is the green line.
The last known position is on the flight path, then
Why not search on East/South China Sea & Bay of Bengal ?

because radar says it deviated from the flightpath and turned around to somewhere in the red box

The initial search efforts did indeed take place in the South China Sea.
Interest moved to the Bay of Bengal after new evidence from military radar surveillance showed that the aircraft had turned west across the Malaysian Peninsula after contact was lost over the South China Sea. It took some time for this evidence to surface because the performance and capabilities of military radar systems are usually closely kept secrets -- presumably a lot of people in the military hierarchies had to sign off on releasing it.
Later still, additional analysis pointed to an area in the south Indian Ocean. It turned out that a single communication system aboard the plane had kept working for many hours after the South China Sea loss-of-contact. This is a satellite-based system that is usually used for routine maintenance messages, not for navigation or accident investigation. It took many weeks to get from "the plane was still alive for many hours" to "it went to the south Indian Ocean", through clever and painstaking analysis of data that the satellite company had originally collected for the purpose of tracking the health and performance of the satellite itself, rather than as a way to locate planes.
Part of the information used was how long it took for the aircraft to respond to the satellite each time it checked in (which gave the distance from the satellite to the aircraft at that time), plus minor variations in the RF frequency the aircraft responded at (which combines to give some information about its heading and velocity). The current search areas are the result of that information combined with "reasonable assumptions" about which speed the aircraft was cruising at during this period.
For some time the best analysis of the satellite data could only say that the last contact must have been either in the south Indian Ocean or somewhere around Afghanistan, but the "northern corridor" was later excluded by more detailed analysis. (It was never considered very likely, since it was much harder to imagine how the plane could stay undetected over land, where it ought to have been in view of many primary radar systems than over the ocean, outside of direct radar coverage).

In particular, the northern corridor pretty much required flying across the India-Pakistan border, and there's no way something as large as an airplane can cross that border undetected.


text:
How long would a cruising aircraft take to crash if everyone spontaneously vanished?
I recently saw a movie in which what appeared to be a Lockheed C-130 Hercules was suddenly without occupants. They did not move or exit the craft, they simply vanished. I assume that the craft remained pressurised, and no modifications to controls were made. I assume that any auto-pilot-like features remained either on or off as they were at the time, unless they have some kind of system to automatically engage in certain situations. At the time of the incident, the aircraft appeared to be cruising.
I am wondering how long it would take for a cruising aircraft take to crash if everyone spontaneously vanished?

The death of Payne Stewart is a real life example similar to your scenario.  https://en.wikipedia.org/wiki/Payne_Stewart#Death  In that case, the aircraft continued flying until it ran out of fuel.

Other cases: the Cornfield Bomber (plane landed in a field with minimal damage after the occupant literally left the aircraft) and this crash of a TBM 900 last year (flew until it ran out of fuel.)

Alternate question: "How long would a cruising aircraft take to crash if everyone awake spontaneously vanished?"

@Michael Awake? As in a scenario in which one person who was asleep wakes up on an otherwise empty plane? Sounds like the plot for a mediocre movie starring Liam Neeson.

@LewisGoddard Yes.  This was actually a reference to the 1995 TV Mini-Series "The Langoliers" starring Dean Stockwell (edit: and Bronson Pinchot). (except there were more like 10 or so people that were sleeping)

Doesn't sound like a very interesting movie, @Lewis.

It's based on a Stephen King novel, actually.

There is a far more important question (and the real deciding factor)
How much fuel is on board?
If left unattended a plane will fly until it runs out of gas quite literally, the more gas in the tanks the longer you have. This has happened on occasion before. The Helios Airways Flight 522 is about as close as you can get to this hypothetical situation in real life. The plane may travel farther (since its lighter) but it will go until its out of gas. The same thing applies to smaller GA planes as well.
This is all of course assuming that the plane is not intercepted before running out of gas. Helios 522 was intercepted by F-16's before it crashed and they visually established that the crew was incapacitated (although a flight attendant tried to save the plane). I don't know what the procedure is for interceptions like this but if the plane were headed for a highly populated area they may not let it run out of fuel.

Another good example: https://en.wikipedia.org/wiki/1999_South_Dakota_Learjet_crash

If the autopilot was on, it's a question of how much fuel is on board as related in another answer (unless high ground was in the way).
If the autopilot is off, even if in perfect trim, the aeroplane will usually gradually drop a wing (this process will start within 15-30 seconds) and develop an ever steepening spiral dive and crash at high speed into the ground.
Sometimes something different has happened, perhaps if a dead pilot has his hands on the controls, but in most cases there is insufficient stability for it to remain wings level for long without pilot input.
I'm thinking of an example in the States where an airliner's wing sliced through the cabin of a light aircraft and cut the three occupants into two. That aircraft managed to land itself intact in a school playing field I think it was, with blood covering the fuselage and wings, but no fuselage top and no visible occupants.
Also, in a small plane the trim might be affected by people disappearing (due to a change in CG) but I think the usual result would be to drop a wing as related.
I am not aware of any systems that would turn an autopilot on automatically if it was off. Finally, many light aircraft only have wing leveller autopilots, so in this case, even if it was out of trim on the elevators, it would take longer (perhaps much longer) to crash, it just might fly long enough to run out of fuel, assuming no mountains were in the way.

Another example of a light airplane (albeit a military one) in which the occupant actually did vanish (he ejected after the aircraft entered a spin) is the so-called cornfield bomber. After the pilot ejected, the aircraft recovered from the spin on its own and landed wings-level with minimal damage in a field. It was repaired and returned to service. And that was a fighter, which typically has much less aerodynamic stability than non-aerobatic civilian aircraft.

@reirab: I don't know about the details, but I would bet a considerable amount that on the day of the "Cornfield Bomber" event the weather was calm and no gusts were shaking the airplane.

Many thanks for the grammer correction edits

I would just like to add that in the case of an aircraft entering a spiral dive there is no guarantee it will reach the ground in one piece. It may break up in the air, due to either excessive G forces, or a structural failure caused by exceeding VNE (never exceed speed). This depends on the aircraft type but would not be helped by going downhill with cruise power set.

Your decapitation accident was the 1986 Cerritos incident but the Piper did not land, it fell. The NTSB report says "‘The Piper PA-28 was destroyed by the collision and ground impact ... The pilot and two passengers in the Piper were found in the remains of the
airplane’s cabin; they were strapped in the left front seat, the right front seat, and the right rear seat. All three occupants had been decapitated".  See http://www3.gendisasters.com/files/files/newphotos2/cerritos_cal_piper_aircraft_wreckage.jpg (wreck, not occupants)

Not sure if this is the same accident or not, the photograph I saw was where the aircraft was relatively intact

@PhilipJohnson: Well, that Piper was relatively intact following ground impact, compared to the DC-9 it collided with (which went into an uncontrollable nosedive and disintegrated when it hit the ground).

I remember reading about another one--GA aircraft, a drug runner, the pilot jumped once he was intercepted.  The plane continued on until it ran out of fuel.  Someone involved (it's been too long since I read about it to remember who) was trying to get permission to shoot it down as it was heading for a city.  It was not shot down, it flew over the city and went down at sea when the fuel ran out.


text:
Could the Wright brothers fly across the US today?
If the Wright brothers were still alive (and in very good health for their age), could they fly one of their aircraft across the United States today?
Specifically, I'm looking at the Wright Model B, a commercially-produced biplane with a maximum speed of 45 mph, a range of 110 miles, and no radio on board.  It was originally produced in 1910, while the first flight across the US (with plenty of stops) was in 1911.
Could a pilot with a Wright Model B use modern airports?  Could they navigate?  Could they keep to their designated airspace?  Could they do all they needed to do to fly in an FAA-approved manner?

there is a flying replica with an FAA registration number

@ratchetfreak, that's quite a find!

it was in the wiki article and I just googled "FAA registry N3786B"

@ratchetfreak, somehow that didn't occur to me...

N3786B - a Wright B Flyer...with a Lycoming engine?!? I seem to hear a whirring sound coming from the general direction of Dayton..! (Of course, according to the registration doc this engine produces zero horsepower and zero thrust, so perhaps more realistic than I originally thought... :-)

I'm going to say no, simply due to the aircraft having what I am going to assume is a very low service ceiling thereby rendering impossible a flight across the Rockies or New Mexico.

It's possible, but it would be difficult under today's regulations.
Restrictions (regulations):

Avoid any controlled airspace that requires talking to ATC
For the sake of argument I'll pretend we have no radio on board, so no class B, C, or D airspace.
(You COULD call the controlling agency and coordinate with them, but let's just pretend we don't have a cell phone either.)

Avoid any airspace within a mode C veil
Because presumably we don't have a transponder on board we can't cross mode C veils.

Avoid any restricted/special use airspace
Duh.

Comply with any other restrictions noted on the chart
I did this in 10 minutes - I may have screwed up a little.

Fuel Reserves
This is the one that makes it tough.
With no wind 110 miles at 40MPH (the cruise speed) is ~2.75 hours endurance - I assume that's to empty tanks (which is how it's usually quoted for aircraft).
The FAA requires at least a 30 minute fuel reserve per FAR 91.151, which means we can fly for 2.25 hours (90 statute miles, 78.2 nautical miles) before we need to land. All legs need to be under that. (It's possible a flight like this could get a waiver from the FAA, but let's assume nobody applied for one.)

Restrictions (Other):

Refueling
Where possible legs should end at airports that have fuel available.
(This isn't a hard "must" since presumably the Wright 1B can burn whatever kind of gasoline we can find once we're on the ground).

Airports
I'm excluding private / restricted airports from consideration as landing spots (again, we'll pretend our pilot has no cell phone and therefore can't coordinate landing access at these fields).

Simplifying Assumptions:

Simple fuel burn
Not having numbers for this aircraft I'm assuming fuel burn will average out such that the aircraft's endurance on all legs is about 2.75 hours (78.2 nautical miles with no wind). This simplifies the planning

There is no wind
(Or if there is, it's always a tailwind.)

There's an aviation GPS (or something like Foreflight) onboard
Frankly I wasn't going to spend an hour looking for landmarks.
You could probably manage the flight by dead reckoning if you had to though.

The Wright Model B can climb high enough to clear any obstacles/terrain
Again, not having numbers for the aircraft (service/absolute ceiling) I'm just making the assumption to simplify things.

So if we put all that together can we plan this flight?
What do you think I did with the first half of my lunch hour?

This is one possible route - there may of course be others
I believe I met all the restrictions, if I screwed up I'm sure someone will edit the flight plan (or come up with a different route).

A Note on Performance
As I mentioned in the assumptions I didn't have performance data available for the 1B when I laid out this route. Some folks helpfully pointed out in comments that there are flying replicas of the 1B.  These don't appear to be "exact reproduction" replicas, but I was able to find some performance data on them.
Given the maximum altitude in the performance figures (2,000 feet MSL) it would probably not be possible to fly the route plotted above with the reproduction equipment available (several legs are well above 2,000 feet MSL), and I would assume the original 1B had comparable performance.

I'm curious as to the longest leg of that route?  How close to the 78.2 nautical mile limit do you cut it?  Did you have a program generate the route for you or was it by hand?

At what altitude do you have it crossing the continental divide?

@Gabe I'm not sure what the highest altitude on the route was (not sure if Skyvector can tell you that), but there are definitely a few spots where you'd be near 11,000 or 12,000 feet on this route (you could reroute to avoid them or find more gentle slopes, or alternately move the whole route to the north where there's lower terrain). As noted in simplifying assumption #4 I didn't take climb performance or service ceiling for the 1B into account in this example - it's mainly leg length and airspace avoidance.

@MooingDuck I cut it pretty close in at least one spot: The leg between KLCG and KONL is 77.1 nautical miles according to skyvector (it's worth noting however that there are 2 other airports you could stop at to shorten that leg). I also found one error in the route (now corrected in the link above) where I had a leg over the limit for airspace avoidance (around Idaho National Laboratory). I generated this route by hand (I basically picked one east coast airport, one west coast airport, and plotted the great-circle line, then added waypoints as needed to meet the constraints).

Since they have a GPS, why no cell phone?  The question is about flying it "today"...  Also, with such short legs they could just call from the airport to coordinate Eden without one.

Did you take wind into account?  40 mph = 35 kts.  77.1 nautical miles with a 10 kt headwind...so 25 kts ground speed = ~3.08 hours - you ran out of fuel.

@DavidWilkins you wait out the wind before you lift off of course

@ratchetfreak not insensible, given your altitude is going to be a couple of hundred feet above the surface

@Lnafziger The practical implications of #4 are "Stay the heck away from Class B airspace" but the FAA calls it a "Mode C veil" in the AIM - probably because of places where it's not coterminous with the outer ring of the class B airspace). The no cell phone/airspace coordination restriction is mainly because I fly in an area where you get laughed at if you try such things (and because it's not a hard route to plan if you can land at airports in class D airspace - where's the challenge?! :)

Have you ever tried flying into an airport without a radio?  They are normally surprisingly helpful, even at busy (non-class-b) airports!

I have flown small Cessna airplanes in different directions across the United States starting from Wichita, KS. As I recall, when heading west, there are 3 routes available - the northern, central and southern routes. These generally follow the routes of major highways or railroads. My recollection is that the southern route - which generally follows Hwy 40 past the big crater had the lowest altitude requirements. Of course, finding fuel stops might be a problem.  I believe Stephen Coonts also flew this route in his Stearman biplane, the "Cannibal Queen".

You can fly coast to coast without once speaking to ATC or landing in a towered field. Sure, around major cities there are areas where you need a transponder and/or a radio to legally enter but the majority of airspace in the US is still uncontrolled.
In fact, it would be much easier and less risky than in the old days given modern handheld gps  units and weather reporting. In the old days there was no weather information, pilots could easily find themselves flying into poor visibility. In the old days there were few reliable road maps, much less anything aviation related, nowdays handheld GPS units and printed charts make navigation simple.
These days you can hop from one airfield to another and know where you are going, how long it will take to get there, and what conditions you can expect along the way. There's also many places to refuel or get maintenance. Personally I think Orville and Wilbur would be pleased with what they would find.

So, in particular, you expect that you'd always be able to stop for more fuel after at most 110 miles?

Not necessarily no. However, you'd have a lot more fuel availability than you would have 100 years ago. To do this for real you may have to plug in a few gaps with some sort of support.

You mentioned road maps. Back at that time, there weren't many roads either, hence not many maps. Construction of Interstate Highway System started in 1950s.

@farhan Something something "federal airway system" something something big giant arrow with a light on it. (Filed under: "Obscure stuff you'll probably never need to know in the real world!")

If Orville and Wilbur reappeared today, along with the original Flyer, I expect the FAA would issue an exemption to pretty much everything in about 5 minutes. Also, every pilot in the hemisphere would be watching rather than working thus eliminating the conflicting-traffic issue.
However, they would have a problem starting around 105 West - small geographical inconvenience called the Rocky Mountains. You could possibly pick a route through various valleys but it's unlikely the original design (engine or airfoil) would work at that altitude. And one good gust of wind down the valley will knock it right out of the sky. History might have been quite different if the Wrights were from Denver.
Take the Wrights for a spin in an SR-71 instead.

It's probably easier to find a Wright Model B in flyable condition than an SR-71.

I think NASA / Dryden have a couple, unless they are also in museums. A century-old Flyer B would be very rickety - I'd prefer to build a new one, shouldn't take more than a couple of days. But you were Wilbur/Orville, which  would you choose? A ride in your own invention or in the pinnacle of aerospace engineering?

According to SR-71.org the last flight of the NASA SR-71's were in October 1999. According to the same site the Air Force retired theirs in 1990, brought a few back in 1995, and then finally retired them in 1998. As far as "What would you take the Wright's up in - shoot, just about anything would be good. How about a 747 where they could get up, walk around, get a good view, fly across the Pacific...or put 'em in the back set of something like an old F-4, put it vertical, and punch the throttles. Elevator - going UP..! :-)

Or the back of the An-225 Mriya, with the first flight taped out on the floor. A '71 still looks way cooler than anything we have today. Maybe an F-117, but it can't go Mach 3.3

They'd get a real kick of E2E Starship if that ever becomes a thing :)

The below answer is probably wrong.  I had thought the elevation at the Continental Divide (at least 4421 feet) would be an obstacle.  However, according to Wikipedia's list of altitude records, an aircraft described as a "Wright biplane" reached an altitude of 8471 feet in October 1910.  It is unclear exactly what model was used, though from the date it was very likely a Model B or some variant thereof.  It could have been a Model R, which appears to have been a high-performance variant of the Model B, "designed for speed and altitude competitions"; apparently two examples of the Model R were present at the 1910 International Aviation Tournament where the 8471-foot record was set.
I'll leave this answer here for a couple days for the correction, then delete it.
Original answer:
No, they could not.
Piggybacking on the data found by voretaq7 and following the issue noticed by paul and gabe: according to this data, a similar aircraft has a maximum altitude of about 2000 feet MSL.  On the other hand, according to this table, the lowest elevation on the Continental Divide in the US is 4421 feet.

You can't really use that maximum altitude since it is a completely different airplane.  From the same page:  "Modern engineering and materials were used to design and build an airplane that would look like a Model B but meet modern airworthiness standards. The result was a robust aircraft with a steel structure and a modern aircraft engine. Its empty weight is 3,400 lbs., compared to the 1,400 pound loaded weight of the machine on which it’s based."

@Lnafziger: Good point, thanks for noticing that.  After further research it appears that Wright aircraft were indeed capable of much higher altitudes; see my edit.

authors: Bob Jarvis - Слава Україні